Osteoporosis is loss of calcium from bone resulting in weakened bone structure. Osteoporosis increases the risk of fracture of vertebral bodies. According to the Osteoporosis Foundation, ten million people have osteoporosis, including 45% of women over 50 years of age.
An estimated 700,000 osteoporosis-related vertebral compression fractures occur annually, resulting in 150,000 hospitalizations. In this type of fracture, the top of the vertebral body collapses down with a greater relative collapse in the front, thus producing “wedged vertebrae,” a “Dowager's hump,” a shortening of height, etc. The resulting change in height and spinal alignment can lead to serious health problems, including chronic or severe pain, limited function and reduced mobility, loss of independence in daily activities, decreased lung capacity, difficulty in sleeping, etc. Further, studies show that a first osteoporotic fracture makes it five times more likely for further fractures to occur.
Vertebroplasty and kyphoplasty are both minimally invasive interventional procedures for treating osteoporotic fractures. Vertebroplasty is defined as a percutaneous procedure, in which a cement-like material (such as, for example, poly-methyl-methacrylat, PMMA) is injected through a needle directly into a fractured bone. U.S. Pat. No. 7,122,205 entitled “Apparatus and Methods for Delivering Compound into Vertebrae for Vertebroplasty”, the entire contents of which are hereby incorporated herein by reference, describes one example of a vertebroplasty solution which provides bone cement into a vertebrae.
U.S. Pat. No. 6,990,368 entitled “Method and Apparatus for Virtual Digital Subtraction Angiography”, the entire contents of which are hereby incorporated herein by reference, includes an example of a mobile x-ray system used for imaging in conjunction with a vertebroplasty treatment. Such a system has several disadvantages. For example, the mobile unit is on wheels, which provides a less rigid structure for precise 3D image reconstruction; as the mobile unit is on wheels, it can carry only low power x-ray tubes; no soft-tissue imaging can be performed with such an angiographic system; and although it is mobile, it is difficult to move into any precise position around a patient.
Kyphoplasty includes one step in addition to the vertebroplasty procedure. Prior to injecting the cement-like material into the fractured bone, a special balloon is inserted and gently inflated inside the fractured vertebrae. The goal of this step is to restore height to the bone, thus reducing deformity of the spine. Published United States Application 2005/0228397 entitled “Cavity Filling Device,” the entire contents of which are hereby incorporated herein by reference, discloses an example method and apparatus for performing a kyphoplasty treatment.
Both vertebroplasty and kyphoplasty procedures are used to stabilize a vertebral fracture and provide immediate pain relief. Both procedures can both effectively treat hemangiomas of the vertebral body and may be palliative in patients with malignant pathologic fractures. Over 195,000 fractures have been treated with balloon kyphoplasty as of Oct. 31, 2005, and approximately 7,400 physicians worldwide have been trained to do the procedure. Results from clinical studies show that both procedures are safe and effective with low complication rates.
However, fractures of the vertebrae have traditionally been more difficult to manage and treat than broken bones in the hip or wrist, etc. The traditional treatment for fractures of the spine caused by osteoporosis, for example, has included pain reduction (medication), bed rest and bracing. Surgery on the spine is extremely difficult and risky, and has typically not been used to treat vertebral fractures associated with osteoporosis, except as a last resort.
Over the past 5-10 years, vertebroplasty and kyphoplasty have been considered as clinically accepted minimally invasive procedures to treat osteoporotic or metastic vertebral fractures. However, until now, there has been no agreement which imaging modality is best to guide and control the interventional procedural steps of vertebroplasty and kyphoplasty. While most operators rely on fluoroscopic imaging, others prefer CT (Computed Tomography) imaging, especially with the use of CT-fluoroscopy (real-time CT imaging with 2-4 images per second and slice thicknesses of 1-10 mm).
Both procedural imaging techniques, however, have several limitations. For example, with fluoroscopy alone, paravetebral soft-tissue is not visible and the cement-like material has difficulties being seen. With CT guidance alone, the real-time imaging may not be sufficient to follow the injection of the cement-like material in either the vertebroplasty or the kyphoplasty procedures. Furthermore, there is limited access to the patient and substantial radiation to the doctor when utilizing the CT-fluoroscopy procedure.